[time-nuts] Opamp Phase noise: OPA653 additional measurements

[Bob Camp]

Hi

Did you do any temperature stabilization on the op amps?

Bob

On Apr 17, 2012, at 5:25 AM, Bruce Griffiths wrote:

> Subsequent measurements using an improved technique has allowed the true flicker phase noise characteristics of  a pair of OPA653 opamps to be determined.
> 
> Opamp
>    Gain 1x (6db folled by 6 db attenuator consisting of a 50 ohm resistor in series with the output of the opamp and the 50 ohm load resistor)
>    Signal input level: + 10dBm
> 
> OFFSET    Opamp PN (dBc/Hz)    Measurement system PN (dBc/Hz)
> 
> 1                -148                                -161
> 
> 10              -161                                -172
> 
> 100            -164                                -177
> 
> 1000          -164                                -179
> 
> Source: 10MHz low phase noise OCXO removed from a Thunderbolt amplified by a QBH9816 amplifier.
> 
> Conclusion: FET opamp PN in the flicker region can be quite low despite its somewhat higher baseband flicker noise than that of some bipolar input opamps.
> 
> Bruce
> 
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